Backplane Optical Interconnects Speed Past Copper

摘要

The limitations of copper become more apparent when trying to move data at gigabit throughput. When running digital signals with clock rates over 20 GHz for any distance, the solution is fiber. System interconnects already incorporate fiber, and deployments like Verizon's FiOS use fiber f°r the last-mile connections. Custom fiber chip-to-chip and board-to-board interconnects have made the rounds, but the technology is gaining more ubiquity among these applications. Standards like VITA 66.4 (see "Will Optics Spell the Death of the Copper Backplane?" at electronic design.com) are driving vendors to deliver products like Samtec's FireFly product family (Fig. 1). FireFly actually addresses copper and fiber with data rates up to 28 Gb/s. A common connector is used to plug in modules that handle a dozen serial links via copper or fiber micro-ribbon cable. The protocol-agnostic system can handle Ethernet, InfiniBand, FibreChannel, and PCI Express. Key to its design is the implementation of a vertical-cavity surface-emitting laser (VCSEL) array.